The present invention is directed to a drilling tool made up of an axially extending hollow cylindrically-shaped holder and a core drill bit. The holder and the drill bit are detachably connected together with one of them telescoping into the other. Projections are provided on one of the holder and the drill bit and engage into recesses on the other for providing a rotatably locked connection.
For reasons of economy, it is known in drilling tools to arrange the core drill bit, incorporating diamond grains, on a holder so that the bit can be detached for purposes of replacement, since the drill bit is exposed to heavy wear. Accordingly, screw connections are used, however, they have the disadvantage that to detach the tool bit, a considerable force is required involving the use of auxiliary tools.
Such a drilling tool is disclosed in DE-A1-32 40 263 and includes a hollow cylindrically-shaped holder and a core drill bit detachably mounted on the holder. Projections in adjoining regions of the holder and the core drill bit connect the bit to the holder so that the holder and bit can be rotated as a unit. A clamping ring, inserted externally in a groove extending circumferentially in the region of the projections, is provided for the axial connection of the holder and the drill bit. A considerable problem with this known drilling tool involves the removal of the clamping ring for replacing the drill bit. In the use of the drilling tool, drilled material can become fixed in the base of the groove, so that the clamping ring does not adequately seat within the groove. During operation, this problem can cause the automatic disengagement of the clamping ring. Another disadvantage involves the impaired stability of the adjoining regions of the part containing the projections.